A ceramic honeycomb structure which is utilized as a catalyst carrier, a filter or the like for exhaust gas purification is prepared through respective steps of extrusion, drying and firing, which is required enlargement for the purpose of the exhaust gas purification of a large car, a construction machine, a ship or the like.
When the extrusion of a large honeycomb formed body is performed in a lateral direction, there has been the problem that the honeycomb formed body is deformed due to its own weight. To solve the problem, the extrusion of the large honeycomb formed body is performed in a downward direction (gravity direction).
In Patent Documents 1 and 2, there are disclosed methods of performing extrusion of ceramic formed bodies in a downward direction. Additionally, in Patent Document 3, there is disclosed an extrusion forming machine in which a plunger type extruder is provided in a two-stage screw type extrusion forming machine. A kneaded material kneaded by the two-stage screw type extrusion machine is extruded in a downward direction by the plunger type extruder. Furthermore, in Patent Document 4, a vertical extruder including a screw is disclosed. In Patent Document 5, there is disclosed a continuous extrusion forming apparatus including a chamber drum having a first space portion extending in an extruding direction and a second space portion extending from a downstream side of the first space portion in a downward direction.